Copper conductive paint has been used in combination with precious metals for many years. Reference is made to the following U.S. Pat. Nos. 3,293,501; 3,776,769; 3,827,891; 3,935,366; 4,084,314 and 4,354,311, as being representative of this art.
The combined use of copper and copper oxide in the form of CuO or Cu.sub.2 O is disclosed in U.S. Pat. Nos. 4,072,771; 4,172,919; 4,323,483; and 4,521,329. U.S. Pat. Nos. 3,902,102 discloses a copper conductive paste disposed upon a ceramic substrate.
A paper presented by co-applicant, Dr. Kuo, to the International Society of Hybrid Microelectronics (ISHM) in 1981, entitled "Adhesion of Thick Film Copper Conductors," relating to alumina substrates, provides useful background data. Also a paper presented by Naomichi Suzuki et al. to the ISHM in 1984, entitled "Application of Porcelain Steel Substrate Thick Film Conductors in Japan" discloses the advantages of a porcelain steel substrate over printed circuit boards (PCB) or epoxy steel substrates. The above referenced patents and publications comprise the closest known prior art.